1. Field of the Invention
The present invention relates to an ancillary instrument set for the reconstruction of the posterior cruciate knee ligament by drilling one or two parallel tibial insertion channels.
2. Discussion of Background Information
Generally, the posterior cruiate knee ligament is reconstructed by inserting a synthetic ligament or one or more natural tendons after drilling one or two tibial channels from front to back. It is necessary to check the exit point to avoid damaging the popliteal vascular and nerve structures during drilling.
This essential precaution entails either checking by a supplementary posterior surgical operation, or using a protective system that is introduced from the front into the intercondylar fossa to meet the posterior surface of the upper end of the tibia. Nowadays, the posterior cruciate knee ligament can also be reconstructed routinely under open surgery or more effectively using an arthroscope without arthrotomy.
It will be seen in this context that reconstruction using an arthroscope makes a cedain number of demands on the system for locating and fitting the posterior cruciate ligament. In particular, it is necessary to have an anatomically correct profile for the protective element as well as ensure that the dimensions of the protective elements are adapted to the narrowness of the front entry so that the protective element of the instrument can remain fixed in place while drilling the two parallel tibial insertion channels.
There is at least one ancillary instrument set for fitting posterior cruciate knee ligaments. This is an instrument that comprises a relatively wide, italic "S" shaped spatula which forms the rear protective element within the articulation, and which is used together with the support arm of a aiming block with two parallel drill tubes. When the support arm has been mounted on the handle of the instrument, the aiming tubes direct the drills to meet the distal end of the spatula. Using this wellknown frontal approach, the spatula is introduced through the intercondylar fossa to behind the posterior surface of the tibia. This protects the popliteal vascular and nerve structures while drilling the tibial insertion channels used for attaching the internal posterior and external posterior ends of the prosthetic ligament that is used for repairing the posterior cruciate knee ligament.
This design of spatula has a number of drawbacks, in particular:
the spatula, approximately 14 mm, is too wide and, when this spatula is introduced through the intercondylar fossa, it displaces all the capsule and ligament structures from the posterior surface of the tibia. PA1 it is not always easy, and indeed sometimes proves impossible, to introduce the two parts of the ligament into the tibial channels and then to slide them along the special groove on the internal surface of the spatula. For the reason described above, the spatula is very often encumbered with fibrous tissues that have been displaced while it is being introduced to the posterior surface of the tibia. Recovery of the sheathed metallic wire that is used to pull the prosthetic ligament into its final position is, therefore, made very unpredictable. PA1 furthermore, this type of ancilliary instrument has been designed exclusively for ligment reconstructions of the posterior cruciate knee ligament under open surgery, and it is not at all suitable for fitting the posterior cruciate knee ligament using an arthroscope as is widely used today. It is generally accepted that a reconstruction using an arthroscope causes considerably less trauma than a classic operation, to the extent that fitting a posterior cruciate knee ligament using an arthroscope could become part of a mobile surgical service. PA1 firstly, at least one bent, hollow tube mounted on an extension which leaves the ends of the bent tube(s) free. The extension fixes rigidly into the handle to which it is fixed by a locking screw. The bent tubes are curved in such a way that they can form together with a rectilinear wire guide tube which replaces the drill after the transtibial channel(s) have been drilled, a continuous channel for guiding a metallic loop used to draw the posterior cruciate knee ligament from the anterior surface of the tibia to the femur insertion point. PA1 and, secondly, a mounting arm at the end of which is fixed a block with parallel drill tubes aligning and guiding the drill and the wire guides in the same plane perpendicular to the plane defined by the axes of the handle and the extension and oriented so that the axes of the drill tubes intersect the end(s) of the bent tube(s).